This invention relates to a semiconductor laser device.
In recent years, semiconductor laser devices have been expected as light sources for optical communication, laser printers, instrumentation etc. In exciting the semiconductor laser devices, a method of carrier injection has been employed owing to such many advantages that a high light conversion efficiency is generally attained and that the optical output can be readily modulated by directly controlling the injection current.
In case of exciting the semiconductor laser device by the method of carrier injection, it is common practice to put the device into the so-called stripe-geometry laser with a narrowed active region in order to permit the operation of the device with a low threshold current and to facilitate the control of the oscillation mode of the laser.
Concrete examples of the stripe-geometry laser are described in U.S. Pat. Nos. 3,920,491, Re. 29,395, etc.
This semiconductor laser device includes a narrow elongated semiconductor region of the same conductivity type as that of another semiconductor region lying in the vicinity of the active region of the laser device. The elongated region extends in depth from the surface of the device to the vicinity of the active region. A surface semiconductor layer of the opposite conductivity type covers the entire surface of the device except for the elongated region.